1. Field of the Invention
The present invention generally relates to filter design, and more particularly to an OTRA-based circuit.
2. Description of Related Art
An operational trans-resistance amplifier (OTRA), having the dual input-and-output characteristics of the well-known operational transconductance amplifier (OTA), becomes one of the most prospective active elements in the field of analog circuit design. The operational trans-resistance amplifier (OTRA) has the following input-and-output relationships: (i) the two + and − terminal input voltages, V+=V−=0, (ii) the output voltage, Vo=(I+−I−)Rm in which Rm is the trans-resistance of an OTRA, and I+ and I− are the two + and − terminal input currents, (iii) very low input impedance, and (iv) very low output impedance. Based upon the above two sets of input-and-output characteristics, it is apparent that an OTRA is the dual of an OTA and vice versa. In addition to this, the main advantage of eliminating the parasitics at the input port of an OTRA due to virtually grounded input terminals is an extra benefit and very attractive for designers.
Hence, several distinct OTRAs have been proposed in the literature since 1992. So do many different kinds of analog circuits, such as integrators, immittance simulators, oscillators, square/triangular waveform generators, monostable and bistable multivibrators, first-order and second-order all-pass filters, and other second-order single-function and multi-function and high-order filters. A universal biquad filter using four (two more) capacitors was presented. However, none of the elliptic Cauer filters using OTRAs has been presented. Elliptic Cauer filter is a better choice than other kinds of filters for meeting the stringent cut-off rate of a very narrow transition band, under the restriction of a finite order.